It is common for a hydraulic actuator such as a linear hydraulic motor to include some type of flow control valve, such as a check valve, at either end of the cylinder component of the hydraulic motor. The flow control valve provides a signal to a switching or directional control valve. The check valve includes a movable valve component that is displaced when the piston component of the hydraulic motor engages the valve component at the end of the piston stroke. A typical situation is where the piston component engages the displaceable valve component of the check valve, causing the valve component to unseat and directing hydraulic oil to a directional control valve. The directional control valve reverses the flow of hydraulic oil to the hydraulic motor, causing the piston component to reverse direction.
It is well known in the art to position a check valve in a cylinder end wall of a linear hydraulic motor so that the piston component longitudinally displaces the valve component in the direction of piston travel. U.S. Pat. No. 4,709,805, entitled "Drive/Frame Assembly for Reciprocating Floor Conveyor," discloses a hydraulic motor having a check valve installed in an end wall of a cylinder component of the hydraulic actuator.
U.S. Pat. No. 4,712,467 discloses a hydraulic motor having a check valve positioned within a piston rod of the motor. U.S. Pat. No. 5,325,763, entitled, "Internal Check Valve," discloses an actuator having a similar design with a check valve within the piston rod. The foregoing patents utilize the same concept of having a check valve opened upon engagement of the piston with a cylinder end wall.
U.S. Pat. No. 5,315,916, entitled, "System of Linear Hydraulic Motors," discloses an actuator with an externally-actuated check valve.
In some applications, it may not be practical to design a check valve, or other type of valve, into the end wall of a cylinder component. For example, the cylinder component end wall may form a ball for a ball and socket support, which universally mounts the cylinder component to another structure. In such an application, it may be necessary to reposition the valve out of the ball end of the cylinder component, yet where the valve can still function to control hydraulic oil flow upon engagement of the piston component with the cylinder end wall. The present invention is directed to just such an application.